USE tempdb;

DECLARE @data

TABLE (

input_month DATETIME NOT NULL,

price MONEY

);

INSERT @data

VALUES ('20090101', $50.00),

('20090201', $58.00),

('20090301', $65.00);

SELECT Days.output_date,

D.price

FROM @data D

CROSS

JOIN (

VALUES (00), (01), (02), (03), (04), (05), (06), (07), (08), (09),

(10), (11), (12), (13), (14), (15), (16), (17), (18), (19),

(20), (21), (22), (23), (24), (25), (26), (27), (28), (29), (30)

) DayOffset (n)

CROSS

APPLY (SELECT DATEADD(DAY, DayOffset.n, D.input_month)) Days (output_date)

WHERE MONTH(Days.output_date) = MONTH(D.input_month);

edit: Fixed!